Field of the Invention
The present invention relates to a manufacturing method of a press-formed article, a press-formed article, and a press forming apparatus.
Description of the Related Art
Hitherto, there is known a technology of manufacturing frame members for automobiles by press forming applied metal plates. In this application for the frame members for automobiles, there is an increasing need for a metal plate constant in the plate thickness as well as a metal plate reinforced by partially forming a thickened portion increased in a plate thickness. A technology of manufacturing a structural component partially increased in the thickness in this way by press forming a metal plate is disclosed in Japanese Patent Application Laid-Open No. 2011-161941 (JP 2011-161941 A).
A method of preparing a flat plate member on which a microbead in a wave shape constructed by a continuous protruded and recessed portion is formed, and press forming the flat plate member for manufacturing an automobile pillar is disclosed in JP 2011-161941 A. This method can be used to press the microbead in the thickness direction for increasing the plate thickness, thereby manufacturing the partially thickened pillar.
The manufacturing method of a pillar disclosed in JP 2011-161941 A includes bending to the flat plate member, thereby forming the microbead in advance, and pressing the microbead to form the thickened portion. In this case, strain is generated by stretching the material in the bending for forming the microbead before the pressing, and, as a result, the thickness is decreased in the plate material. Therefore, even if the microbead is pressed in the subsequent process, an intended thickened amount is not realized, and large decreases in the thickness are locally generated, which may constitute start points of cracks in the press-formed article. The method disclosed in JP 2011-161941 A may not be used to appropriately obtain a desired shape as described before.